Aurelius Ambrosius is the rightful king of Britannia. He has built up an army like the Roman legions of old, but he knows it is not enough. If he is to win the support of his fellow Britons he must find the Sword of Albion to prove his right to the kingship. But others are looking for that sword, among them, the "proud tyrant", Vortigern. Aurelius goes on a perilous quest through crumbling Roman cities, and high into the Pennines while Vortigern tries everything to stop him, including making a fake sword, and while these two Britons battle for supremacy, the Angles and Saxons, led by Hengest, are invading from the North Sea.